The present invention relates generally to the field of imaging systems such as those used in medical diagnostics. More particularly, the invention relates to an integrated system that makes use of different modalities in a complementary fashion to permit feedback to surgeons and other medical professionals of physical conditions of a subject, particularly during interventionary procedures.
A wide variety of imaging systems have been developed and are presently in use in the medical field. The systems may be generally categorized in a series of xe2x80x9cmodalities,xe2x80x9d with each modality being characterized by its particular physics, control, utility, and so forth. For example, magnetic resonance imaging (MRI) systems are commonly employed for producing images of gyromagnetic material within a subject of interest. Over recent years, such systems have become particularly refined in producing high quality and reliable images of internal organs and other particular types of tissue, in various orientations within the subject. X-ray-based techniques have also grown considerably from their initial roots in analog systems utilizing photographic film. Modern x-ray-based modalities include digital x-ray systems which produce electronic data sets representative of picture elements or pixels within an array that can be reconstructed into a useful and high quality image. Other x-ray-based techniques include computed tomography (CT) systems in which x-ray radiation traverses a subject, impacts a detector, and resulting signals are reconstructed by a computer into a useful image through the subject. Still other modalities include positron emission tomography (PET), ultrasound, and so forth.
While the various modalities of imaging systems used in the medical field have improved dramatically in recent years, and continue to improve, they have tended to develop in isolation. MRI systems, for example, are typically used for specific purposes, such as imaging soft tissues. X-ray-based modalities are often used in other situations for which MRI systems are less suitable. In such systems, where images are desired of tissues or anatomies which cannot normally be identified or contrasted from neighboring structures, various approaches may be employed to provide the desired contrast, typically through the use of liquid contrast agents which are injected into the patient prior to the examination sequence. These contrast agents, however, do not necessarily provide the particular tissue identification desired, may not be retained for the time and in the locations desired for the entire procedure, and may cause complications for certain patients. Other techniques have been developed to attempt to identify probes, catheters, and the like, through the use of one or another modality system. Such probes, for example, may include coils which respond to the pulse sequences of MRI systems, to provide feedback to a surgeon during a surgical intervention such as catheterization, and so forth.
In certain procedures, it would be useful to provide additional feedback to medical personnel of the state of tissues and anatomies based upon a combination of imaging modalities. For example, during catheterization, angioplasty, and similar procedures, MRI systems may permit a surgeon to identify soft tissues through which a probe is inserted, but are not necessarily well suited to imaging tissues indicative of the actual location of the probe. Because surgical interventions happen in real time, currently available technologies for separate modality imaging are simply ill suited to providing this type of information and feedback. There is a need, therefore, for an improved technique for supplying anatomical images to medical professionals which overcomes the limitations of separate modalities such as MRI and x-ray-based systems.
The present invention provides an integrated imaging system designed to respond to these needs. The technique may be applied as a combination of various different imaging modalities, but is particularly well suited to combining MRI systems with x-ray-based systems, such as digital x-ray fluoroscopy systems. The systems are combined in a complimentary and cooperative manner, such that real-time images may be produced of soft tissues through use of MRI imaging sequences, while images of more dense or contrasting tissues and objects may be produced through the x-ray system. The systems may be physically combined by positioning a specially-adapted support structure for a digital x-ray apparatus in an MRI system. Separate images may be produced by the two systems, with the desired anatomy of soft tissues being projected on a screen associated with the MRI system, while the x-ray image is displayed on a separate screen. Alternatively, the system may be adapted to register and combine the images to provide real-time feedback of all of the structures of interest, thereby making use of the strength of the combined modalities in the resulting imaging. In addition to real-time imaging, the system may be employed to produce images which are registered or associated with one another, with the still images being available for viewing, storage, transmission, and so forth.